THE SOCIAL LIFE OF THE LOWER ANIMALS. 527 
which serves them as a locomotive garment, but scarcely do they 
essay to use their delicate limbs, than they claim the aid and 
lodge in their first hotel; restless and unquiet, they soon abandon 
it for another home, and then reéstablishing themselves are con- 
demned to perpetual seclusion. 
That which adds to the interest which these feeble and timid 
beings inspire, is that at each change of their domicile, they 
change their costume, and also, arrived at the end of their pere- 
gtinations, they wear a virile toga, not to say a wedding dress. 
It is only under this last envelope that the sexes appear, for up to 
this time they have thought little of family cares. 
Most of the worms which have the form of a leaf or of a rib- 
bon, are subject to these peregrinations accompanied with changes 
of costume, and those which do not arrive at their final stage, 
generally die without posterity. 
Not the least interesting is the fact that these parasites do not 
inhabit indifferently such or such organs of their host; all begin 
modestly by the almost inaccessible mansard roof, and end their 
lives in the large and spacious apartments of the first floor. At 
first they care only for themselves, and are contented, under the 
name of Scolex or vesicular worms, with connective tissue, muscles, 
the heart, the ventricles of the brain, or even the ball of the eye ;* 
later they busy themselves with the cares of their families, and 
occupy the larger organs, as the alimentary and respiratory tracts, 
always in free communication with the outer world; they have a 
horror of being shut up, and their offspring reclaim an existence 
1n the broad world.+ 
It is not always easy to indicate the identity of those person- 
ages which visit one day the saloons, in embroidered dress, the 
next the most obscure closets in a beggar’s costume. 
ere is a last category in which are found those who claim aid 
during their whole existence ; penetrating at once into the body 
of their host, they do not move, but lodge there from the cradle 
to the tomb. : 
It is only a few years since we did not suppose that a parasite 
could live in any other animal than that in which we found it. 
All helminthologists, with few exceptions, regarded the intesti- 
* All the sexual Cestoids. 
t Most of those worms called ectop.rasites, as the Tristomas, etc. 
